Who The Ancients Were

Almost everything fits:

the Ancients disappeared;
every planet with Ancient ruins has slinkers;
slinkers are telepathic;
Aycharaych is telepathic;
he is also the last Chereoinite;
he confirms that the Chereionites were the Ancients;
he does not say what made them withdraw.

Well, he would not want to admit that his people had created telepathic pets that were their downfall. (See previous post.) So the questions, "Where did the Ancients go?" and "Where did the Chereoinites go?" have the same answer. And apocalyptic hopes placed in the return of the Ancients are futile. But Axor might nevertheless learn something important by studying their ruins.

What does not fit, as correspondent Sean M. Brooks has pointed out, is this. It was learned on Aeneas that, at close range, Aycharaych can read the mind of any being irrespective of species or language. (Is this even theoretically possible? We must accept it for current story purposes.) Despite this, Dominic Flandry is surprised later in the series to discover the extent of Aycharaych's mental powers. Of course, some explanation of this discrepancy could have been written into the series. Like Shakespeare's scripts, the stories and novels of the Technic Civilization History must ultimately be regarded as unfinished works in progress.